Add better error pages

templates/csrferror.jade

@@ -24,7 +24,8 @@ html(lang="en")
                 li A malicious user has attempted to tamper with your session
                 li Your browser does not support cookies, or they are not enabled
               | If the problem persists, please contact an administrator.
-            a(href=path) Return to previous page
+            if referer
+              a(href=referer) Return to previous page
 
     include footer
     mixin footer()

templates/httperror.jade

@@ -0,0 +1,36 @@
+mixin notfound()
+  h1 Not Found
+  p The page you were looking for doesn't seem to exist.  Please check that you typed the URL correctly.
+mixin forbidden()
+  h1 Forbidden
+  p You don't have permission to access <code>#{path}</code>
+mixin genericerror()
+  h1 Oops
+  p Your request could not be processed.  Status code: <code>#{status}</code>, message: <code>#{message}</code>
+doctype html
+html(lang="en")
+  head
+    include head
+    mixin head()
+  body
+    #wrap
+      nav.navbar.navbar-inverse.navbar-fixed-top(role="navigation")
+        include nav
+        mixin navheader()
+        #nav-collapsible.collapse.navbar-collapse
+          ul.nav.navbar-nav
+            mixin navdefaultlinks(path)
+          mixin navloginlogout(path)
+
+      section#mainpage.container
+        .col-md-12
+          .alert.alert-danger
+            if status == 404
+              mixin notfound()
+            else if status == 403
+              mixin forbidden()
+            else
+              mixin genericerror()
+
+    include footer
+    mixin footer()